Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$183.50	8.208%	$198.5617	$198.56	$198.55	$198.60
Purchase #2	$169.46	10.250%	$186.8297	$186.83	$186.85	$186.80
Purchase #3	$60.97	4.454%	$63.6856	$63.69	$63.70	$63.70
Purchase #4	$139.47	13.850%	$158.7866	$158.79	$158.80	$158.80
Purchase #5	$82.82	8.472%	$89.8365	$89.84	$89.85	$89.80
Purchase #6	$148.25	7.174%	$158.8855	$158.89	$158.90	$158.90
Purchase #7	$42.54	3.365%	$43.9715	$43.97	$43.95	$44.00
7 purchase totals =	$827.01		$900.5571	$900.57	$900.60	$900.60